The Engineer's and Mechanics Encyclopædia: Lithography.

The Engineer's and Mechanics Encyclopædia,
comprehending practical illustrations of the machinery and processes employed in every description of manufacture of the British Empire.
With nearly Two Thousand Engravings.
By Luke Hebert, civil engineer, edifor of the History and Progress of the Steam Engines, Register of Arts and Journal of Patent Inventions, etc.
In two volumes.
VOL. II.
London: Thomas Kelly, 17, Paternoster Row.
MDCCCXXXVI (1836).

(Tekstiin lisätty kappaleita lukemisen helpottamiseksi. // Some paragraphs added to the original text for making reading easier.)The art of transferring from stone, writings or drawings made thereon; which is quite of modern invention. Unlike other kinds of printing, this is strictly chemical, and is in consequence called in Germany, chemical printing. A drawing is made on the stone, either with ink containing oleaginous matter; or with chalk, containing similar substances, but in a more concentrated and indurated state. The drawing is then washed over with water, which sinks into those portions of the stone that are untouched with the grease of the drawing. A cylindrical roller, charged with printing ink, is then passed all over the stone, and while the drawing receives the ink, the rest of the stone is preserved from it by the water on account of the greasy nature of the ink.

This art is said to have been invented by mere accident, by Alois Senefelder, of Munich, who being an author, and too poor to publish his works, tried various plans, with copper-plates and compositions, with a view to becoming his own printer. In the course of his experiments, he found that a composition of soap, wax, and lamp-black, formed an excellent ink for writing with on plates; as, when dry, it became firm and hard, and resisted aquafortis. He wanted facility, however, in writing backwards on the plates; and that he might exercise this at less expense, he procured some pieces of Kilheim stone, as a cheap material, on which, after polishing their surfaces he might practise. Having been desired by his mother to take a list of some linen about to be sent to be washed, and having no paper at hand, he wrote it out on a piece of stone with his composition. When he was afterwards about to efface his writing, it occurred to him that impressions might be obtained from, it; and after he had bit in the stone with aquafortis, diluted with ten parts of water, after letting the fluid stand five minutes over it, he proceeded to apply printing ink to the stone, for which purpose he first applied a printer's ball, but after some unsuccessful trials, he made use of a thin piece of wood covered with fine cloth, and with this he perfectly succeeded in taking impressions.

It appeared to him that this new mode of printing was of very considerable importance; and he therefore, though with great difficulties, persevered in improving it, and in attempting its application to practical purposes. He soon found that it was not necessary to have the letters raised above the stone; but that the chemical properties which keep grease and water so effectually separate from each other, were quite sufficient for his purpose. He afterwards bestowed much labour and assiduity in constructing the proper press, and other apparatus for printing. The first essays to print for publication were some pieces of music executed in 1796; afterwards he attempted drawings and writings. He still however found great difficulty in writing backwards, and this led him to think of the process of transfer; and the use of dry soap, which was found to leave permament traces which would five impressions, naturally led to the mode of chalk drawings.

In 1799, after having made many improvements, Senefelder obtained a patent privilege for the electorate of Bavaria. In 1803, he introduced his discovery into Vienna, where he obtained a similar grant for ten years. The invention spread, though slowly, into France and Italy, but it was not brought over to England until 1801, when M. Andre d'Offenbach, a merchant in London, succeeded in introducing it only to a very limited extent. While the war lasted, the employment of the lithographic art was chiefly confined to the quarter-master general's office at the Horse Guards, where it was used for printing the plans of battles, and maps of the seat of war. After the peace the art was revived, and there are now in England, as well as in all parts of the continent, numerous establishments, where it is practised with great excellence; and it is difficult to say at the present time, whether the German, French, or English artists, have obtained the pre-eminence. We shall now proceed to explain the several processes of the art.


The Stones, and the manner in which they are prepared to receive the drawings.

The stone most used in England is found at Corstan, near Bath: it is one of the white lias beds, but not of so fine a grain, nor so close in texture as the German stone, and therefore inferior; but it is good for transfers, and does tolerably well for ink drawings or writings. All calcareous stones may be used in lithography, because they imbibe grease and moisture; but a stone entirely calcareous does not answer well; there should be a mixture of alumina and silex. One of the most certain indications of lithographic properties, is the conchoidal fracture: all stones of this kind will be found good, if they are also hard, have the fineness of grain, and the homogenousness of texture that are necessary. It is however said that none have yet been found equal to those obtained from the quarries of Solenhofen, near Pappenheim in Bavaria, and that the lithographers of eminence in Paris use no other.

In order to sustain the pressure used in taking impressions, a stone, 12 inches square, ought not to he less than 1¾ inch thick, and, this thickness should increase with the area of the stone. The stones are first sawn to a proper size, and are then ground smooth and level by rubbing two of them lace to face, with water and sand. They must be very carefully examined with a straight edge, to ascertain that they are perfectly level in every direction. This applies only to the side which is afterwards to receive the drawing, as the natural division of the stone is sufficiently true for the back. When the stones have thus been ground perfectly level, they are well washed, to free them from any of the coarser grains of sand which may have been used in smoothing them. They are then placed on a board over a trough, and they are again rubbed face to face with sand and water, but with a sand of much finer texture than that previously used. The greatest care must be taken to have the sand sufficiently tine; and for this purpose it must be sifted through a small close sieve, as a single grain of sand of a coarser texture than the rest will scratch the stone, and these scratches will afterwards appear in the impression taken from the stone.

When the stones have been rendered sufficiently fine, and their grain sufficiently smooth, they must then be carefully washed and afterwards wiped dry with a clean soft cloth. This is the plan adopted to prepare the stones for chalk drawings , but to prepare them for ink drawings or writings, the following method is the best: — After the process just described has been completed, the stones are well washed to get rid of the sand, and they are then rubbed to together, face to face, with powdered pumicestone and water. After they are made perfectly smooth, they are again washed and wiped dry, and are then separately polished with a large piece of pumicestone.


To clean the stones after they have been fully used, sand is strewed over the surface, which is sprinkled with water and rubbed with another stone, until the writing or drawing upon it has completely disappeared. It must then be washed in aquafortis, diluted with twenty times its bulk of water; and the stone is then prepared for a new drawing or writing, by being rubbed with fine sand or pumicestone as before. The longer drawings remain on stones the deeper the ink or the chalk penetrates into their substance, and consequently the more of the stone must be ground away to remove them; this is also more necessary with ink drawings or writings than with chalk, owing to the greater fluidity and consequent penetrability of the former.

The substances used by the artist upon the stone, are either lithographic ink, or lithographic chalk. The former has been described under the article Ink, (which see;) but —

The Ink for making transfers should be somewhat less burned, and therefore softer than that used for writing or drawing directly upon the stone.

Lithographic chalk should have all the qualities of a good drawing crayon. It should be even in texture, and carry a good point. The following proportions are recommended: 1½ oz. of common soap, 2 oz. tallow, 2½ oz. virgin wax, 1 oz. shell-lac. The rest of the process is the same as in making the ink. Less black should be mixed with the chalk than with the ink, its only use being to colour the drawing, that the artist may see the lines he traces. When the whole is well mixed, it should be poured into a mould and very strongly pressed, to expel any air that may collect in bubbles, which would render it spongy.


Mode of drawing.

Previous to drawing or writing, the stone must be well wiped with a clean, dry cloth. The ink is rubbed with water, like Indian ink, and is almost wholly used on the polished stone. The chalk is used only upon the grained stone; the polished surface of the other would not hold it. In drawing with ink, a gradation of tints is obtained either by varying the thickness of the lines, or their distances from one another, as in engraving. The ink lines on polished stones, being solid and unbroken throughout, receive the printing all over; and if the lines be drawn as fine and as uniform as they are usually on copper, the print from them will be in no respect inferior; hut it requires a greater degree of skill to execute as well upon stone as is usually done upon copper or steel.

In using chalk, the grained stone should be very carefully dusted, and the utmost attention be paid to prevent any lodgment of the smallest particle of greasejupon the surface; personal cleanliness is therefore absolutely necessary to the perfection of his work, especially in chalk drawings. The chalk is used upon the stone precisely in the same manner as crayon upon paper; but it is of essential advantage in lithography to finish the required strength of tint at once, instead of going over the work a second time, the stone being impaired in its ability to receive the second lining clearly, by the absorption of the first. Some practice is requisite to use the chalk cleverly, as there has been no chalk hitherto made that will keep so good a point as is desirable. There is likewise some difficulty experienced in obtaining the finer tints sound in the impression; and in order to obtain the lighter tints properly, it will be necessary to put the chalk in a rest, as^the metal port crayon is too heavy to draw upon the stone. The editor, who sometimes practises, is in the habit, before he commences his subject, of pointing 20 or 30 pieces of chalk, stuck in quill holders, and placing them beside the stone in a little box, taking them up successively as the points become worn off, so as to avoid, if possible, the cutting off chalk during the work, which endangers the soiling of the stone. When a very sharp and, delicate line is required, he sharpens the point of the chalk upon paper, by pushing it forward in an inclined position, and twirling it round at the same time between the fore-finger and thumb. As the chalk softens by the warmth of the hand, it is quite necessary to have several pieces, to be able to change them. Some artists cut their chalk into the wedge form, as being stronger. Those portions that break off in drawing should be carefully taken off the stone by a camel's hair brush.


Preparation of the stone for printing.

The drawing being finished on the stone, it is sent to the lithographic printer, on whose knowledge of his art depends the success of the impressions. The first process is to etch the drawing as it is called. This is done by placing the stone obliquely on one edge, over a trough, and pouring over it very dilute nitric acid. It is poured on the upper part of the stone, and runs down ail over the surface. The stone is then turned, and placed on the opposite edge, and the etching water being collected from the trough, is again poured over it, in the same manner. The degree of strength, which is usually about one per cent, of acid, should be such as to produce a very slight effervescence; and it is desirable to pass the etching water two or three times over the darkest parts of the drawing, as they require more etching than the lighter tints. Experience alone can, however, guide the lithographer in this department of the art, as different stones, and different compositions of chalk, will be differently acted upon by the acid; and chalk drawings require a weaker acid than the ink. The stone is next to be carefully washed, by pouring clean rain water over it, and afterwards with gum water; and when not too wet, the roller charged with printing ink is rolled over it in both directions — sideways, and from top to bottom — till the drawing takes the ink. It is then well covered over with a solution of gum Arabic in water, of about the consistency of oil. This is allowed to dry, and preserves the drawing from any alteration, as the lines cannot spread, in consequence of the pores of the stone being filled with the gum.

After the etching, it is desirable to leave the stone for a day, and not more than a week, before it is printed from. The effect of the etching is first to take away the alkali mixed with the chalk or ink, which would make the drawing liable to be affected by the water; and secondly, to make the stone refuse more decidedly to take any grease. The gum assists in this latter purpose, and is quite essential to the perfect preparation of the sur face of the stone.


Printing.

When the intention is to print from the stone, it is placed upon the platten or bed of the press, and a proper sized scraper is adjusted to the surface of the stone. Rain water is then sprinkled over the gum on the stone, which, being dissolved gradually, and a wet sponge passed lightly over all, the printer works the ink, which is on the colour table placed beside him, with the roller, in all directions, until it is equally and thinly spread on the roller. The roller is then passed over the whole stone, care being taken that the whole drawing receives a due portion of ink; and this must be done, by giving the roller an equal motion and pressure, which will of course require to be increased, if the drawing does not receive the ink readily.

When the drawing is first used, it will not receive the ink so readily as it will afterwards; and it is frequently necessary to wet the stone, and roll it several times, before it will take the ink easily. After this takes place, care must be taken not to wet the stone too much; the dampness should not be more than is necessary to prevent the ink adhering to the stone where there is no drawing.

After the drawing is thus rolled on, the sheet of paper is placed on the stone, and the impression taken. Upon taking the paper off the stone, the latter appears to be quite dry, owing to the paper having absorbed the moisture on the surface; it must therefore be wetted with a sponge, and again rolled with ink, the roller having been well worked on the colour table before being applied.

During the printing, some gum must always remain on the stone, although it will not be visible, otherwise the ink will be received on the stone as well as on the drawing, by which the latter would be spoiled; so that if by too much wetting, or by rubbing too hard with the sponge, the gum is entirely removed, some fresh gum water must be laid on. If the stone has in the first instance been laid by with too small a quantity of gum, and the ink stains the stone on being first applied to it, gum water must be used to damp the stone, instead of pure water. Sometimes, however, this may arise from the printing ink being too thin, as will afterwards appear.

If some spots on the stone take the printing ink, notwith standing the above precautions, some strong acid must be applied to them with a brush, and after this is washed off, a little gum water is dropped in the place. A steel point is here frequently necessary to take off the spots of ink.

The edges of the stone are very apt to get soiled, and generally require to be washed with an old sponge after rolling in; they must also frequently have an application of acid and gum, and sometimes must be rubbed with pumicestone.

If an ink is too thin, and formed of a varnish not sufficiently burned, it will soil the stone, notwithstanding the proper precautions are taken of wetting the stone, and preparing it properly with acid and gum; and if, on the other band, the ink is too thick, it will tear the lighter tints of the chalk from the stone, and thus destroy the drawing. The consideration of these circumstances leads at once to the —


Principles of the Printing. —
The accidents just mentioned arise at the extreme points of the scale at which the printing inks can be used, for it is evident that the only inks that can be used are those which are between these points; that is, thicker than that which soils the stone, and, at the same time, thinner than that which takes up the drawing. Lithographers are sometimes unablo to print in very hot weather, the reason of which may be deduced from the foregoing. Any increase of temperature will diminish the consistency of the printing ink; the stone will therefore soil with an ink which could be safely used at a lower temperature; hence a stiffer ink must be used. Now, if the temperature should increase so much that the stone will soil with any ink at all less thick than that which will take up the drawing, it is evident that the printing must cease till a cooler temperature can be obtained; for as the drawing chalk is effected equally with the printing ink, the same ink will tear up the drawing at file different degrees of temperature. This, though it sometimes occurs, is a rare case; but it shows that it is desirable to draw with a chalk or ink of lees fatness in summer than in winter; and also, that if the printing room is in winter artificially heated, pains should be taken to regulate the heat as equally as possible.

Other Difficulties in Printing, not referable to the foregoing general Principle. —
If the pressure of the scraper be too weak, the ink will not be given off to the paper in the impression, although the drawing has been properly charged with it. Defects will also appear from the scraper being notched, or not correctly adjusted, or from any unevenness in the leather or paper. After printing a considerable number of impressions, it sometimes happens that the drawing takes the ink in dark spots in different parts. This arises from the printing ink becoming too strongly united with the chalk or ink of the drawing, and if the printing be continued, the drawing will be spoiled. The reason of this is easily ascertained. The printing ink readily unites with the drawing, and being of a thinner consistency, it will, by repeated applications, accumulate on the lines of the drawing, soften them, and make them spread. In this case, it is necessary to stop the printing, and let the stone rest for a day or two, for the drawing to recover its proper degree of hardness. If the drawing should run smutty from any of the causes before enumerated, the following —

Mature for cleaning the Drawing while printing must be used. —
Take equal parts of water, spirits of turpentine, and oil of olives, and shake them well together in a glass phial, until the mixture froths; wet the stone, and throw this froth upon it, and rub it gently with a soft sponge. The printing ink will be dissolved, and the whole drawing will also disappear, though, on a close examination, it can be distinguished in faint white lines. On rolling it again with printing ink, the drawing will gradually re-appear, as clear as at first.

Bleached Paper unfit for Lithographic Printing. —
Accidents sometimes occur in the printing from the qualities of the paper. If the paper have been made from rags which have been bleached with oxy-muriatic acid, the drawing will be incurably spoiled after thirty impressions. Chinese paper has sometimes a strong taste of alum; this is so fatal, as sometimes to spoil the drawing after the first impression. When the stone is to be laid by after printing, in order that it may be used again at a future period, the drawing should be rolled in with a —

Preserving Ink; as the printing inks would, when dry, become so hard, that the drawings would not take fresh printing ink freely. The following is the composition of the printing ink: — Two parts of thick varnish of linseed oil, four parts of tallow, one part of Venetian turpentine, and one part of wax. These must be melted together, then four parts of lamp black, very carefully and gradually mixed with it, and it must be preserved for use in a close tin box.

Autographic Ink, or that which is suitable for transferring on to the stone the writings or drawings which have been executed on paper prepared for that purpose, should possess the following properties. The ink ought to be mellow, and somewhat thicker than that used immediately on stone; so that when it is dry on the paper, it may still be sufficiently viscous to cause adherence to the stone by simple pressure. The following is the composition. Dry soap, and white wax free from tallow, each 100 drachms, mutton suet, 30 drachms, shellac and mastic, each 50 drachms, lamp black, 30 to 35 drachms; these materials are to be melted in the way described for lithographic ink. (See Ink, Lithographic.)


Autographic Paper. —

The operation by which a writing or drawing is transferred from paper to stone, not only affords the means of abridging labour, but also of producing the writings or drawings in the same directions in which they have been traced; whereas, when they are executed immediately on stone, they must be performed in a direction opposite to that which they are eventually to have. Thus it is necessary to draw those objects on the left, which, in the impression, are to be on the right hand. To acquire the art of reversing subjects when writing or drawing, is both difficult and tedious; while, by the aid of transparent, and of autographic paper, impressions may be readily obtained in the same direction as that in which the writing or the drawing has been made.

In order to make a transfer on to stone of a writing, a drawing in lithographic ink, or in crayons, or an impression from a copper plate, it is necessary 1st, that the drawing or transcript should be on a thin and flexible substance, such as common paper; 2d, that it should be capable of being easily detached from this substance, and transferred entirely on to the stone, by means of pressure. But as the ink with which a drawing is traced penetrates the paper to a certain depth, and adheres to it with considerable tenacity, it would be difficult to detach them perfectly from each other, if, between the paper and the draw ing, some substance was not interposed, which, by the portion of water which it is capable of imbibing, should so far lessen their adhesion to each other, that they may be completely separated in every point.

It is to effect this that the paper is prepared, by covering it with a size, which may be written on with facility, and on which the finest lines may be traced without blotting the paper. Various means may be found of communicating this property to paper. The following preparation has always been found to succeed, and which, when the operation is performed with the necessary precautions, admits of the finest and most delicate lines being perfectly transferred, without leaving the faintest trace on the paper. For this purpose, it is necessary to take a strong, unsized paper, and to spread over it a size prepared of the following materials: starch, 120, gum arabic, 40, and alum, 21 drachms. A moderately thick paste is made with the starch, by means of heat; into this paste is thrown the gum Arabic and the alum, which have been previously dissolved in water, and in separate vessels. The whole is mixed well together, and it is applied warm to the sheets of paper, by means of a brush, or a large flat hair pencil. The paper may be coloured by adding to the size a decoction of French berries, in the proportion of ten drachms.

After having dried this autographic paper, it is put into a press, to flatten the sheets, and they are made smooth by placing them, two at a time, on a stone, and passing them under the scraper of the lithographic press. If, on trying this paper, it is found to have a tendency to blot, this inconvenience may be remedied by rubbing it with finely-powdered sandarac.

Annexed is another recipe, which will be found equally useful, and which has the advantage of being applicable to thin paper, which has been sized. It requires only that the paper be of a firm texture; namely, gum tragacanth, 4 drachms; glue, 4; Spanish white, 8; and starch, 4 drachms.

The tragacanth is put into a large quantity of water to dissolve, thirty-six hours before it is mixed with the other materials; the glue is to be melted over the fire in the usual manner. A paste is made with the starch; and after having, whilst warm, mixed these several ingredients, the Spanish white is to be added to them, and a layer of the sizing is to be spread over the paper, as already described, taking care to agitate the mixture with the brush to the bottom of the vessel, that the Spanish white may be equally distributed throughout the liquid. We will hereafter point out the manner in which it is necessary to proceed, in order to transfer writings and drawings. There are two autographic processes which facilitate and abridge this kind of work when it is desired to copy a fac-simile, or a drawing in lines. The first of these methods is to trace, with autographic ink, any subject whatever, on a transparent paper, which is free from grease and from resin, like that which, in commerce, is known by the name of papier vbgktal, and to transfer it to stone; this paper to be covered with a transparent size: this operation is difficult to execute, and requires much address, in consequence of the great tendency which this paper has to cockle or wrinkle when it is wetted.

Great facilities will be found from using tissue paper, impregnated with a fine white varnish, and afterwards sized over.

In the second process, transparent leaves, formed of gelatin, or fish glue, are employed, and the design is traced on them with the dry point, so as to make an incision; these traces are to be filled up with autographic ink, and then transferred. We will describe, in their proper places, these processes, as well as that of transferring a lithographic or a copper-plate engraving.


Autographic Processes. — To transfer a drawing or writing to stone, it is made with ink on paper, both prepared in the way we have described. A crayon drawing may, on an emergency, be executed autographically; but this mode of procedure is too imperfect to admit of procuring, by its means, neat and perfect proofs; besides, it is as expeditious to draw immediately on the stone.

In order to write, or to draw on autographic paper, a little of the ink of which we have given the composition is diluted with water, taking care to use only rain-water, or such as will readily dissolve soap. The solution is facilitated by slightly warming the water in the cup; and the ink is dissolved by rubbing the end of a stick of it in the manner practised with Indian ink. There should be no more dissolved at a time than will be used in a day, for it does not re-dissolve so well, neither is the ink so good, particularly for delicate designs, after it has been left to dry for several days. This ink should have the consistence of rather thick cream, so that it may form very black lines upon the paper; if these lines are brown, good impressions will not be obtained. A sheet of white paper is placed under the hand while writing, in order that it may not grease the autographic paper.

The stone used for autography should be polished with pumice-stone, and the impressions will be neat in proportion as the stone is well polished. Autographic work may be executed either cold or warm; that is, taking the stone at its ordinary temperature, or making it warm by placing it near to the fire, or exposing it to the heat of the sun; if the first means of warming be used, care must be taken that the fire be not too hot, or it will crack the stone; the temperature given to it should be about that of an earthen vessel filled with lukewarm water. The work may be done, though less perfectly, without warming the stone. When the stone is thus prepared, it is fixed in the press, and the paper on which the writing is made is applied to it. The stone may be rubbed with a linen, slightly moistened with spirits of turpentine; and in every case it is necessary that it be made perfectly clean. The turpentine is left to evaporate; and from five to eight minutes before the paper is applied, it is wetted with a sponge and water on the reverse side to that on which the writing is done, so that the moisture may penetrate throughout every part. The water, however, must not appear on the paper when it is about to be laid on the stone; but any superabundance which may remain on it must Le removed by a pressed sponge. When the paper is brought to the proper state, it is taken by both hands at one of its extremities, and placed lightly and gradually upon the stone, so that there may be no plaits formed in it, and that it may be equally applied over its whole surface. Care must be taken so to fix the scraper that it may bear steadily on the autographic paper; for if it removes it at all it will change the place of pressure, and the lines will be doubled. There should be at band five or six sheets of very even mackle paper, so that they may be changed with each impression. The paper on which the writing or drawing is made being placed on the stone, it is covered with a sheet of mackle paper, and subjected to a slight action of the press; then to a second, a third, or even to more, until it is believed that the writing is perfectly transferred. At each stroke of the press the mackle paper, which has imbibed moisture, is withdrawn, and a dry sheet substituted in its place. All these operations require to be performed with expedition and dexterity, particularly when the stone is warm. The next thing is to detach the autographic paper, which will be found adhering closely to the stone. To effect this, it is well wetted with a sponge, so that every part of it may be perfectly penetrated by the water; it may then be removed with facility, entirely detached from the writing, which will remain adhering strongly to the stone. If this operation, which requires much practice, be well performed, there will not be found the slightest trace of ink remaining on the paper. Should there be any lines not well marked on the stone, they may he retouched with a pen; or, which is better, with a hair pencil and ink; but when this is done, care must be taken that the stone is quite dry. A part of the sizing of the paper may be found dissolved and adhering to the stone; this may be removed by washing or slightly rubbing it with a wet sponge. The stone is then prepared with aqua-fortis, and the impression taken.

Autography is not confined to the transferring of writings or drawings done with autographic ink; by its means a transfer may be obtained from a sheet of ordinary printed paper, and with such exactness, that it would be impossible, excepting to well-practised eyes, to perceive the least difference between that printed in the usual way, and that which was the result of the autographic process. This mode is very useful when it is desired to unite oriental cha racters, which might not be possessed with words, phrases, or lines composed in ordinary typography. In this way have been executed, in the office of the Count M. C. de Lasteyrie, at Paris, (from whose papers on this subject, contained in the Journal des Connaissances Usuelles, and translated by the learned editor of the Franklin Journal, our account of this art is largely indebted,) many pieces, in which the French or the Latin language was intermixed with words or phrases in Chinese or Arabic. In the same way have also been executed typographic maps, in which all the details were lithographic, while the names of places were at first produced by typography, and afterwards by autography. This operation is begun by composing and arranging, in a typographic form, the words, the phrases, or the lines, as they ought to stand. The autographic paper is printed on by this form, and the words in the oriental languages are afterwards written in the spaces which had been left for them; the whole is transferred to a stone, which is prepared for the purpose, and from which the impression is taken in the usual manner. The same mode is pursued in making geographical maps. After having printed the names on autographic paper, the other parts of the map, but without the names, are drawn immediately on the stone; and after havmg printed the names on white paper, the map drawn upon the stone, is printed on this same paper.

Maps, or line engravings on copper, where the work is not very close, may be multiplied in a similar way. For this purpose the plate of copper is covered over with the autographic ink, diluted to a convenient consistence. Instead of the autographic ink, a composition is sometimes used, made of one ounce of wax, one ounce of suet, and three ounces of the ink with which the ordinary impressions in lithography are taken. The whole is warmed and mixed well together, and there is a little olive oil added to the composition, if it is not liquid enough to spread itself over the plate; the plate ought to be warmed as usual. After having taken the impression in the rolling press on a sheet of autographic paper, the transfer may be immediately made on the stone, after having rubbed it with a sponge, dipped in turpentine. It is necessary to give three, four, or even more strokes of the press, increasing the pressure at every successive stroke; the other processes, which we have already described, arc likewise to be followed. It is well to wait twenty-four hours before preparing the stone, in order that it may be better penetrated by the transferring ink; it is then gummed and washed, and is ready for use. This process, which has not yet come much into use amongst lithographers, merits the attention of artists; for it affords the means of re-producing and multiplying geographical charts, and some kinds of engravings indefinitely, so that they might be furnished at a quarter of their present actual value; in fact, all those which are done in lines, or those in which the shadows are boldly executed, are capable of re-producing good impressions by means of autography. The operation becomes extremely difficult when it is necessary to transfer fine line engrav ings; the lines of these are so delicate, and so near to each other, that they either do not take well on the stone, or are apt to be crushed and confounded together by the effect of the pressure. Much practice and address are neces sary to obtain tolerable impressions; and this part of the art requires improve ment. In the office of M. de Lasteyrie, they had succeeded in transferring to stone a small highly-finished engraving, which had been printed on common half-sized paper. After having dry-polished a stone very perfectly, it was warmed, rubbed with spirits of turpentine, and then the engraving was applied to it. This had, however, been previously dipped into water, then covered on the reverse side with turpentine, passed again through the water, so as to remove the superfluous turpentine, and then wiped with unsized paper. In this state the engraving, still damp with the turpentine, was applied to the stone and submitted to pressure, when it afforded very good impressions; the preparation not being applied until it had remained on the stone for twenty-four hours. The difficulties increase, of course, in proportion to the size of the engravings which it is desired to transfer to the stone. Attempts have been made to transfer old engravings; they have, however, succeeded but imperfectly. It would be rendermg an essential service to the art to discover a mode of re-producing old engravings by means of autography; the undertaking presents difficulties, but from the attempts made, success does not seem improbable.


Printing from two or more Stones with different Coloured Inks. —
This is managed by preparing a composition of two parts of wax, one of soap, and a little vermilion. Melt them in a saucepan, and cast them into sticks; this must be rubbed up with a little water to the thickness of cream, and applied to the surface of a polished stone. An impression is taken in the common way from a drawing, and applied to a stone prepared in this manner, and passed through the press, taking care to mark, by means of this impression, two points in the margin corresponding on each of the stones. The artist, having thus on the second stone an impression from the first drawing to guide him, scrapes away the parts which he wishes to remain white on the finished impression. The stone must now be etched with acid stronger than the common etching water, having one part of acid and twenty of water; the whole is then washed off with turpentine: this plan is generally used in printing a middle tint from the second stone; the black impression being given from the first stone, a flat transparent brownish tint is given from the second, and the white lights are where the paper is left untouched. The dots are necessary to regulate the placing of the paper on the corresponding parts of the two stones.